1. Field of the Invention
The present invention relates to a fixed-focus imaging lens that forms an optical image of a subject on an image sensor, such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), and an imaging device that is provided with the imaging lens and performs imaging, such as an imaging device incorporated in a digital still camera, a mobile phone with camera, a PDA (Personal Digital Assistance), a smartphone, a tablet-type terminal, a portable video game player, etc.
2. Description of the Related Art
Along with the spread of personal computers in ordinary homes, etc., digital still cameras that are capable of inputting image information, such as photographed landscapes and portraits, to a personal computer are also rapidly spreading. Further, more and more mobile phones, smartphones and tablet-type terminals are equipped with a camera module for inputting images. The above-mentioned devices capable of imaging use an image sensor, such as a CCD or CMOS. In recent years, such image sensors are becoming more compact, and there are also demands for compact imaging devices and compact imaging lenses to be incorporated in the imaging devices. At the same time, pixel density of such image sensors is also becoming higher, and imaging lenses with higher resolution and higher performance are demanded. For example, performance that can accommodate a high pixel density of 5 megapixel or more, or more preferably 8 megapixel or more is demanded.
In order to meet the above-described demands, an imaging lens formed by a relatively large number of lenses, namely, having a five-lens configuration may be provided. For example, each of U.S. Pat. No. 8,395,851 and U.S. Patent Application Publication No. 20130201567 (hereinafter, Patent Documents 1 and 2, respectively) proposes an imaging lens with a five-lens configuration including, in order from the object side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power.